“The Supreme Court finds no irregularities that could result in the cancellation of the March 18 presidential elections,” said the ruling.
The 22-page ruling validated the result that had been announced on March 23.
That result gave former prime minister Carlos Gomes junior 49 percent of the vote and ex-president Kumba Yala 23 percent.
Yala, was one of those who appealed, alleging massive fraud and calling for the result to be cancelled.
His spokesman Victor Pereira confirmed to AFP the candidate’s previously stated position that he would not be taking part in the second round run-off.
All five candidates issued a joint statement Sunday denouncing the court.
“We do not recognise the fabricated results,” it said.
“The decision of the Supreme Court reveals once again it has chosen the path of injustice. This court lacks balance and moral and professional dignity, that is lamentable.
Yala’s warning that he would take no part in the second round has already provoked fears of unrest in this former Portuguese colony, which has suffered chronic instability and has allowed a cocaine trade to flourish.
Already Friday the country’s electoral commission was forced to postpone election campaigning for the second-round run-off, originally scheduled for April 22, because of the opposition appeals.
A commission official said Tuesday it would announce a revised date on Tuesday.